The invention relates generally to a steerable catheter, and more particularly to a catheter handle having a steering controller for applying tension to a tendon to steer the catheter and a system for maintaining tension on the steering tendon when it is not tensioned by the steering controller.
In many medical procedures, it is necessary to place a catheter at a particular location within the patient""s body. Precise placement of the catheter is more easily accomplished when a steerable catheter is used. Such catheters are typically flexible at the distal end, and the profile at the distal end is deflectable.
Changing the profile of the distal-end region of a steerable catheter typically involves the use of a steering tendon that is housed within the catheter shaft. The steering tendon is usually a wire that has its distal end attached to the distal-end region of the catheter shaft. The proximal end of the catheter shaft attaches to a handle. The proximal end of the steering tendon exits through the proximal end of the catheter shaft and attaches to a steering controller within the handle.
The profile of the distal-end region of the catheter shaft can be deflected from its non-steered configuration by manipulating the steering controller from a neutral position so that the steering tendon is axially displaced in the proximal direction. Axially displacing the steering tendon in the proximal direction places the steering tendon in tension which is reacted by offset and opposing compressive forces within the catheter shaft. These opposing tensile and compressive forces create a bending moment that acts upon the distal-end region of the catheter shaft, preferentially on the side where the steering tendon is attached, thereby deflecting the distal-end region. If the steering controller is released, the distal-end region of the catheter shaft typically springs back to its natural state due to the structure of the catheter shaft, thus moving the steering tendon and the steering controller back to their neutral positions.
It is often necessary to maintain the force exerted on the steering tendon during the course of a medical procedure so as to retain the deflected profile of the distal-end region of the catheter. In some of the existing steerable catheters, maintaining the force exerted on the steering tendon requires the operator to manually hold the steering controller in place. However, it is often difficult for the operator to maintain a constant amount of force on the steering tendon for an extended period of time or while further manipulating the handle.
In other existing steerable catheters, an additional knob attached to the steering controller is used to lock the displacement of the steering tendon at its present position. This knob is used to tighten the steering controller against a friction plate within the handle housing until the resulting friction is sufficient to prevent the steering controller from moving from its present position. Typically, the operator must turn this knob with one hand while the other hand is used to maintain the preferred position of the steering controller relative to the handle housing. Thus, locking the steering controller in other steerable catheters is a two-handed operation.
Steerable catheters that utilize steering tendons can have either single or multiple steering tendons. During the use of a multiple-tendon steerable catheter, manipulation of the steering controller results in the application of tension to one steering tendon, while no force is deliberately applied to any other tendon. Tendon wires in steerable catheters are typically small in diameter in order to conserve catheter lumen space. Tendon wires are usually made of a wire material possessing a high modulus of elasticity and high yield strength so that they exhibit minimal elastic stretch and will not permanently deform under ordinary tensile loads. However, because of their relatively small diameters, catheter tendon wires can be easily bent and are prone to buckling when subjected to axial compressive forces.
The majority of a tendon wire""s length is typically protected from bending by virtue of the inherent rigidity of the surrounding catheter shaft. Further, buckling of a tendon wire within the catheter shaft is unlikely because the tendon wire is typically supported by a dedicated tendon sheath or lumen, or at least by the wall of the main catheter lumen. However, within a catheter""s handle, a tendon wire typically has an unsupported span between the proximal end of the catheter shaft and the steering linkage to which the tendon is attached. When subjected to repeated steering, this span may be susceptible to kinking, which can adversely affect the catheter""s steering performance.
In some existing catheters, the proximal ends of all steering tendons are rigidly affixed to their respective linkage points. As a result, when tension is applied to only one tendon, the other tendons may be forced to bow or kink in response to the catheter shaft""s unavoidable length change. Other steerable catheters attempt to avoid that problem by routing each steering tendon through a hollow stop within the handle""s steering linkage system and affixing a terminal to the proximal end of each steering tendon. In that configuration (see FIG. 1a), all terminals typically butt against their respective stop when the catheter is in its neutral (non-steered) position. When tension is applied to only one steering tendon to steer the catheter (see FIG. 1b), the extraneous length in all other tendons can pass through their respective hollow stop. However, a corresponding gap between the hollow stop and the terminal then exists, resulting in a relaxed steering tendon that may be subject to bowing or kinking (see FIG. 1c).
Hence, those skilled in the art have identified a need for an improved steering system for steering a catheter, and one that reduces or minimizes the slack in steering tendons. The present invention fulfills these needs and others.
Briefly, and in general terms, the present invention is directed to a system in which a steering controller includes a device to maintain the steering tendon in tension when it is not tensioned by the steering controller.
In a first aspect, the invention relates to a system for applying tension to a steering tendon. The tendon has a distal end that is attached to the distal-end region of a catheter shaft and a proximal end that exits the proximal end of the shaft. The system also includes a movable steering controller and means for coupling the tendon to the steering controller. Through the coupling means, movement of the controller in a first direction relative a neutral position increases tension on the tendon and movement of the controller in a second direction relative the neutral position, and opposite the first direction, maintains tension on the tendon.
In a detailed aspect of the invention, the coupling means includes a stop that is disposed at the controller and has the proximal end of the tendon passing therethrough and terminating at a point that is a distance from the stop, and a spring device that has a distal end at the stop and a proximal end attached to the tendon at a location proximal to the stop. In a more detailed aspect, the spring device is in a fully compressed state when the steering controller is in the neutral position and when the steering controller is moved in the first direction. In a further aspect, the spring device is in a partially compressed state when the steering controller is in the neutral position, and the compression increases when the steering controller is moved in the first direction. In another detailed aspect, the spring device extends in length, yet remains in compression, when the steering controller is moved in the second direction. In another detailed aspect, the spring device includes a wire coil that surrounds the tendon between the stop and the proximal end of the tendon. In yet another detailed aspect, the catheter shaft has an inherent bending stiffness and the tension imparted by the coupling means when the controller is in the neutral position has negligible impact on the profile of the catheter shaft.
In a second aspect, the invention relates to a system for steering a catheter shaft. The catheter shaft has a proximal region and a distal-end region and at least one steering tendon that has a distal end attached to the shaft distal-end region and a proximal end that exits the shaft proximal end. The system includes a steering controller. The proximal end of the at least one steering tendon is coupled to the steering controller in such a manner that when the controller is in a neutral position, tension is applied to the tendon. The system also includes means for increasing tension on the tendon when the controller is moved in a first direction away from the neutral position. The system further includes means for maintaining tension on the tendon when the controller is moved from its neutral position in a second direction opposite the first direction.
In a detailed aspect, the means for increasing tension on the tendon includes a spring device that is coupled to the controller at one end, secured to the tendon at the other end, and is adapted to be substantially in a fully compressed state when the controller is moved in the first direction. In another aspect, the means for maintaining tension on the tendon includes a spring device that is coupled to the controller at one end, secured to the tendon at the other end, and is adapted to extend in length, yet remain in compression, when the controller is moved in the second direction.
In a third aspect, the invention relates to a system for steering a catheter shaft. The catheter shaft has a proximal region and a distal-end region and at least one steering tendon that has a distal end attached to the shaft distal-end region and a proximal end that exits the shaft proximal end. The system includes a controller that has the proximal end of the at least one steering tendon coupled thereto and is adapted to move the proximal end of the tendon. The system also includes a spring device that is coupled between the proximal end of the tendon and the controller. The spring device is configured to maintain tension on the tendon. Movement of the controller in a first direction relative to a neutral position increases the tension on the tendon.
In a detailed aspect of the invention, the spring device is secured at one end to the proximal end of the tendon and at the other end to the controller and the spring device is configured to be fully compressed during controller movement in the first direction. In another aspect, the spring device is secured at one end to the proximal end of the tendon and at the other end to the controller and the spring device is configured to extend in length, yet remain in compression, during controller movement in a second direction relative to the neutral position and opposite the first direction. In yet another aspect, the spring device includes any one of a compression spring, tension spring, and leaf spring.
In a fourth aspect, the invention relates to a system for applying tension to a first steering tendon and a second steering tendon. Each tendon has a distal end that is attached to the distal-end region of a catheter shaft and a proximal end that exits the proximal end of the shaft. The system includes a movable steering controller and means for coupling the first and second tendons to the steering controller. Through the coupling means, movement of the controller in a first direction relative a neutral position increases tension on the first tendon while maintaining tension on the second tendon. Also through the coupling means, movement of the controller in a second direction relative the neutral position increases tension on the second tendon while maintaining tension on the first tendon.
In a detailed aspect, the coupling means includes a first stop that is disposed at the controller and has the proximal end of the first tendon passing therethrough and terminating at a point a distance from the first stop, a first spring device that has a distal end at the first stop and a proximal end attached to the proximal end of the first tendon, a second stop that is disposed at the controller and has the proximal end of the second tendon passing therethrough and terminating at a point a distance from the second stop, and a second spring device that has a distal end at the second stop and a proximal end attached to the proximal end of the second tendon. In a more detailed aspect, the first and second spring devices are in a compressed state when the steering controller is in the neutral position and thereby maintain tension on the first and second tendons respectively. In an even more detailed aspect, the catheter shaft has an inherent bending stiffness and the tension imparted by the first and second spring devices when the controller is in the neutral position has negligible impact on the profile of the catheter shaft. In another aspect, the first spring device is in a fully compressed state and the second spring device has extended, yet remains in a compressed state when the controller is moved in the first direction, and the second spring device is in a fully compressed state and the first spring device has extended, yet remains in a compressed state when the controller is moved in the second direction. In a further aspect, the first and second spring devices are in a partially compressed state when the steering controller is in the neutral position, but the compression increases on the first spring device then the steering controller in moved in a first direction and the compression increases on the second spring device when the steering controller is moved in a second direction.
In a fifth aspect, the invention relates to a handle for steering a catheter shaft. The catheter shaft has a proximal region and a distal-end region and at least one steering tendon. The steering tendon has a distal end that is attached to the shaft distal-end region and a proximal end that exits the shaft proximal end. The handle includes a housing that is attached to the proximal end of the catheter shaft. The handle also includes a movable steering controller that is connected to the housing. The handle further includes means for locking the steering controller in place relative to the shell housing. Also included in the handle is means for moving the steering controller from the locked position to a free position. Moreover, the handle includes means for coupling the tendon to the steering controller. Movement of the controller in a first direction relative a neutral position increases tension on the tendon and movement of the controller in a second direction relative the neutral position, and opposite the first direction, maintains tension on the tendon.
In a sixth aspect, the invention relates to a catheter. The catheter includes a catheter shaft that has a proximal region and a distal-end region. The catheter shaft also includes at least one steering tendon that has a distal end attached to the shaft distal-end region and a proximal end that exits the shaft proximal end. The catheter also includes a handle for steering the catheter shaft. The proximal end of the shaft is attached to the handle. The handle includes a housing that has a plurality of alternating protrusions and recesses. The catheter further includes a steering controller that is carried by the handle. The steering controller has a plurality of alternating protrusions and recesses. The proximal end of the steering tendon is connected to the steering controller and the steering controller is adapted to move the proximal end of the tendon. The catheter also includes a spring device that is coupled between the proximal end of the at least one tendon and the controller. The spring device is configured to maintain tension on the tendon. The steering controller is adapted to translate between a locked-position wherein at least one of the steering controller protrusions or recesses is interrelated with at least one of the housing protrusions or recesses, and a free-position wherein none of the steering controller protrusions or recesses is interrelated with any of the housing protrusions or recesses. Movement of the controller in a first direction relative to a neutral position increases the tension on the tendon.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention.